This invention relates to an apparatus and method for preparing fluids used for dialysis procedures.
Dialysis is a procedure for removing waste products from the blood of a patient when the kidneys are unable to do so on their own. Hemodialysis is a form of dialysis in which waste products are directly removed from the blood. The blood of a patient suffering from impaired kidney function is conducted along one side of a permeable membrane in a dialyzer device, while dialysis fluid is conducted along the opposite side of the same membrane. The waste materials that are to be removed from the blood pass with the help of diffusion from the blood of the patient to the dialysis fluid through the permeable membrane.
The dialysate is an aqueous acetic solution which contains various electrolytes. The dialysate generally contains sodium chloride, potassium chloride, calcium chloride, acetate ions, dextrose and other constituents in the same concentration as normal plasma. Urea, creatinine, uric acid phosphate and other metabolites normally eliminated by the kidneys diffuse from the blood of the patient into the dialysate until the concentration of these compounds are the same in the blood and in the dialysate. The volume of dialysate fluid used is much greater than the blood volume. The great disparity in volume and the replenishment of dialysate with fresh fluid insure that the metabolites and excess electrolytes are removed almost completely from the blood.
The dialysate is generally prepared from a dialysate concentrate (which contains sodium ions, potassium ions, calcium ions, magnesium ions, chloride ions, acetate ions, and dextrose), a bicarbonate solution and water. The dialysate concentrate, bicarbonate solution and water are generally combined at, or by, the dialysis machine.
Dialysate concentrates are generally prepared in centralized preparation plants and are then transported to the point of treatment in large kegs or other containers (typically 55-gallon drums). As a result, hospitals or other facilities performing hemodialysis procedures must devote a considerable amount of space for storage of dialysate concentrate. A further disadvantage with the currently prevalent practice of having the dialysate concentrate prepared at a centralized preparation plant and transported to the point of treatment in large containers, rather than preparing the dialysate concentrate at the point of treatment, is the relatively higher costs associated with shipping large containers of dialysate concentrate from the centralized preparation plants to the point of treatment.
As an alternative, dialysate concentrates have been prepared at the point of treatment. These methods have involved combining powders and/or highly concentrated liquid solutions with water in a mixing vessel to form the dialysate concentrate. Although such methods can significantly reduce transportation costs and storage space requirements, they have not been favored because of the relative difficulty involved in accurately combining the powders and/or highly concentrated liquids with the appropriate amount of water, and completely dissolving the electrolytes using conventional mixing apparatuses.
U.S. Pat. No. 4,784,495 discloses a system for preparing a fluid intended for a medical procedure substantially at the time of use. The system includes a reservoir for a source of water, at least one vessel containing a concentrate in powder form, and a concentrate fluid circuit for withdrawing a small quantity of water from the reservoir and passing the water through the vessel containing the concentrate in powder form in order to dissolve the concentrate to produce a concentrate fluid, and for then conducting the concentrate fluid to a primary fluid circuit communicating with the reservoir so that the produced concentrate fluid is mixed with the rest of the water withdrawn from the reservoir. Although this apparatus can reduce storage requirements for dialysate concentrates, and appears to be relatively easy to operate, it is a relatively complicated and expensive apparatus.
Accordingly, there remains a need for a simple, relatively inexpensive, easy-to-operate apparatus for preparing dialysate concentrates from dry powders and/or highly concentrated liquid solutions at the point of use to reduce storage requirements and transportation costs.
The present invention provides a simple, inexpensive apparatus for preparing a dialysate concentrate for use in performing a dialysis procedure. The apparatus includes a vessel, a liquid inlet port to the vessel, an automatically controllable valve for regulating water flow through the inlet port into the vessel, first and second sensing devices for detecting when the liquid has reached a lower liquid level and an upper liquid level respectively, a controller selectively responsive to one of the sensing devices for closing the automatically controllable valve when a selected one of the first and second sensing devices detects that the liquid has reached the lower or upper liquid level respectively, and a switch for selecting to which of the sensing devices the controller is responsive.
The method includes the steps of connecting a source of water to the inlet port, filling the vessel to the predetermined lower liquid level by positioning the switch so that the controller is responsive to the first sensing device and opening the automatically controllable valve, allowing the first sensing device to detect when the predetermined lower liquid level has been reached and signal the controller to shut the automatically controllable valve, adding a predetermined amount of a powder and/or highly concentrated liquid to the vessel, operating the agitator for a period of time sufficient to cause the added powdered and/or highly concentrated liquid to dissolve into and/or mix with the water in the vessel to form a homogeneous solution, filling the vessel to the predetermined upper liquid level by positioning the switch so that the controller is responsive to the second sensing device and opening the automatically controllable valve, and allowing the second sensing device to detect when the predetermined upper liquid level has been reached and signal the controller to shut the automatically controllable valve.
In one aspect of the invention, a dialysate concentrate is prepared from a pre-measured package of dry ingredients and a pre-measured amount of an acid solution.
The invention also provides a simplified method for using the apparatus for preparing a dialysate concentrate. The method and apparatus of the invention are cost effective, save time, decrease storage space requirements, and facilitate easy preparation of dialysate concentrate at the point of use. The apparatus is highly portable, and relatively small and lightweight, so that it can be easily set-up and used at relatively small facilities, such as small clinics. The apparatus is easy to use and can be operated by an individual, without any additional assistance.